T cells play a central role in the immune system against foreign pathogens such as bacteria and viruses, and against abnormal cells such as cancer cells. It is thought that a decrease in the function of T cells due to various causes may lead to increased susceptibility to infection and development of cancer and the like. If replacement or regeneration of immune cells is possible in cases of such diseases, it may act as very effective means for amelioration of the disease state and improvement of a therapeutic effect on the diseases. In such replacement therapy of immune cells, replacement and regeneration of the function of T lymphocytes, which are responsible for cell-mediated immunity, have been strongly demanded. However, no effective therapeutic method has been established so far.
In replacement therapies of T lymphocytes that have been proposed, gene transfer of an antigen-specific T cell receptor (TCR) gene into various lymphoid cells is carried out to allow replacement and activation of specific immune reaction (Non-patent Documents 1 and 2). In these attempts, CD34-positive cells, which are bone marrow progenitor cells, naive T lymphocytes, and the like are used as the cells to be subjected to the gene transfer. However, these have a number of disadvantages such as low ability of ex-vivo self-renewal, low gene transfer efficiency, and difficulty in regulation of differentiation by gene transfer.
Replacement therapies using T lymphocytes induced from pluripotent stem cells such as iPS cells have also been proposed (Non-patent Document 3 and Patent Document 1). In the method for inducing T lymphocytes from pluripotent stem cells, (1) a step of inducing hematopoietic progenitor cells from pluripotent stem cells, (2) a step of inducing CD4/CD8 double-negative cells from the hematopoietic progenitor cells, (3) a step of inducing CD4/CD8 double-positive cells from the CD4/CD8 double-negative cells, and (4) a step of inducing T lymphocytes from the CD4/CD8 double-positive cells, have been proposed.
For the step (1), a method in which a net-like structure sac (ES-sac) is formed from pluripotent stem cells to produce hematopoietic progenitor cells is known (Non-patent Document 4), For the steps (2) and (3), methods in which culture is performed on an OP9-DL1 cell layer in a medium supplemented with IL-7 and Flt-3L are known (Non-patent Documents 5 and 6). For the step (4), a method in which culture is performed in a medium supplemented with an anti-CD3 antibody (OKT-3) and IL-2 is known.
However, the efficiencies of production of T lymphocytes from pluripotent stem cells in these methods are insufficient, and their improvement has been demanded.